1. Field of the Invention
Elongated extensions have long been available for mounting over the regular forks or tines of lift trucks. These have been used to give a further reach to the lift truck. However, such extensions have been troublesome to use and most require much additional manual labor. The present invention contemplates the permanent installment of telescopic sleeve extensions on the tines of fork lift trucks and the power operating of such extensions either to a forward extended position or retracted so the sleeves are substantially coextensive with the regular tines of the lift truck. This eliminates the necessity of a manual putting on and taking off of such extension forks. More importantly this new device permits the operators of lift trucks to convert their forks from longer to shorter forks and vice-versa during operation. The extended forks may be used to reach further out for a load to be retrieved whereafter that load may then be pulled back toward the lift truck to make the truck more stable before the load is fully or entirely removed from its original resting place, and either raised or lowered.
Another feature of the invention is to provide for the stripping of the load from a pallet. For example, many goods or products are often mounted on pallets and then loaded on truck beds. When the truck reaches its destination the loaded pallets usually are then removed by lift trucks. In the past the only way to remove the goods or products from the pallets was by manually removing such goods. As a rule the synchronizing of a suitable labor force with the delivery of goods by truck is very difficult and the result in many instances is that the pallets are left at the site of the consignee. Either the pallets must be expendable or a return trip must be made to retrieve the pallets after they have been unloaded. It is the purpose of this invention to provide for the mechanical unloading or stripping of the pallets of their goods or products at the time of unloading so the pallets may be returned to the shipper immediately.
2. Description of the Prior Art
A patent search was made and the following patents were found and believed to have some bearing on the patentability of the subject device.
The U.S. Pat. No. 2,973,879 to Gibson shows fork extensions 36 and 38 joined by a cross tie member 40. These extensions are powered in or out on the regular forks 24 and 26 of a lift truck by hydraulic cylinders. The Gibson device is unusual in that in addition to having powered fork extensions it also has means for moving the entire lift assembly fore and aft by a scissors linkage. The operation of the scissors linkage in its extending direction by the cylinder 48 causes a simultaneous extension of the fork extensions 36-38-40. Conversely when the cylinder 52 is energized to cause a retraction of the extensions there is a simultaneous retraction of the scissors linkage by reason of the chains 42 which join the fork extensions with the scissors linkage. The operator does not have the ability with this mechanism to extend or retract the fork extensions without, at the same time, extending or retracting the lift mast.
The U.S. Pat. No. 3,561,628 to Melin provides for the separate hydraulic shifting of fork sleeves on the forks of a fork lift. The Melin sleeves are not the same as fork extensions but rather are means for angularly adjusting a load on the forks to permit uniform stacking of the loads lifted by the forks. Without such means it would be necessary to reposition the entire lift truck to square up a stack.
The U.S. Pat. No. 3,416,686 to Penrod shows a haystacker having fully retractable forks. The forks are extended to carry such items as hay bales and when the bales are set on top of a stack, the forks are retracted. The "aligning strips" 24, 26, 30 and 32 form a vertical face which presses against the bale and prevents the stack from being jostled while the forks are retracted.
The U.S. Pat. No. 3,512,672 to Carpenter shows power operated fork extensions on a shelf stacking crane. The forks are hinged as well as having extensions to permit the loads to reach the shelves.
The U.S. Pat. No. 3,549,035 to Soper causes a member within a wedge shaped fork to move fore and aft therein to cause roller bearing members to be raised to or retracted from the surface of the forks. A load carried by the forks will slide off the forks easily when the rollers are exposed.
The U.S. Pat. No. 2,536,068 to Lehmann shows a raisable load carrier consisting of a fixed section, a section slidable endwise thereon outwardly and inwardly and power means between the sections, controlled at the driver's station for operating the slidable section in each direction.
Although others have previously employed power extensions for the fork tines of lift trucks, no one had previously employed the simple front carried linkage of applicant to effect extension or retraction of the cross joined sleeves on the regular fork tines for reaching farther forward with the forks at the discretion of the operator and at a time during operation of the truck. Certainly no one of these prior devices contemplated the stripping of a pallet in combination with power extended sleeve extensions on the forks of a lift truck.